Evaporator circuit



S p 1954 D. E. HILLIKER ETAL EVAPORATOR CIRCUIT Filed Sept. 27, 1952Inventor-s: Ddnald E.Hillike1-, Stephen Balogh,

Their- Attorneg.

w Y ,m n M Y A r ll/ 214 57/11/114 Patented Sept. 14, 1954 UNITED STATESPATENT OFFICE EVAPORATOR CIRCUIT Donald E. Hilliker and Stephen Balogh,Erie, Pa.,

assignors to General Electric Company, a corporation of New YorkApplication September 27, 1952, Serial No. 311,876

3 Claims. 1

This invention relates to refrigerating systems and more particularly tosuch systems including defrosting arrangements.

In many household refrigerators, the evaporator for cooling the foodstorage compartment is exposed to the air within the compartment and isoperated at a temperature below the freezing point of water. As aresult, the moisture in the air within the food storage compartmentcondenses on the evaporator and collects thereon in the form of frost.This layer of frost on the surface of the evaporator has an insulatingeffect, reducing the efficiency of the evaporator in cooling-the foodstorage compartment. It is accordingly necessary to remove this frostfrom time to time in order to prevent too serious a reduction in theoperating efficiency of the refrigerating apparatus. In many cases, thisdefrosting is accomplished manually by stopping operation of thecondensing unit and placing trays of warm Water on the refrigeratedsurfaces of the evaporator. Defrosting in this manner is a somewhattime-consuming and disagreeable operation. This manual operation may beavoided by supplying heat in some manner to the evaporator or the tubingof which the evaporator is formed. In some cases, where such adefrosting system is incorporated, there may occasionally be erraticoperation and it is desirable that this be avoided.

It is an object of this invention to provide an 0 improved refrigeratingsystem incorporating a defrosting arrangement.

It is another object of this invention to provide an improved defrostingarrangement includ ing an improved arrangement for insuring circulationof refrigerant in the desired direction.

It is a further object of this invention to pro vide an improvedrefrigerating system including an improved arrangement for minimizingsurging of refrigerant into the header and suction line.

Further objects and advantages of this invention will become apparent asthe following description proceeds and the features of novelty whichcharacterize this invention will be pointed out with particularity inthe claims annexed to and forming a part of this specification.

Incarrying out the objects of this invention, a refrigerating system isemployed which includes a flooded evaporator having a header, and acontinuous generally depending conduit connected at both ends thereto.The continuous conduit is connected to the header at one end through avertical section which communicates with the header below the level ofliquid refrigerant therein. A trap is provided at the bottom of thisvertical section, and in accordance with this invention, a check valveis provided between the trap and the remainder of the conduit. Thischeck valve minimizes surging of refrigerant upwardly through theaforementioned vertical section and into the header and suction line.

For the better understanding of this invention, reference may be had tothe accompanying drawing in which Fig. 1 is a side elevation view of aportion of the refrigerator incorporating an embodiment of thisinvention.

Fig. 2 is a perspective, partially phantom, view of the evaporator.

Fig. 3 is a sectional enlarged view of the check valve structure.

Referring to the drawing, there is shown a refrigerator cabinetincluding an outer wall I and a spaced inner wall or liner 2, the innerwall 2 defining a food storage compartment 3. The space between theinner and outer walls is filled with a suitable insulating material l.The access opening of the food storage compartment is closed by a door5.

In order to cool the food storage compartment 3, an evaporator 6 ismounted in the upper portion of this compartment. The evaporator 6includes a supporting wall structure, including a bottom horizontal wallI, a rear vertical wall 8, a top Wall 9, and two end walls It] and I I.The wall structure defines a compartment l2 for the storing of frozenfoods and the like.

The evaporator 6 is of the flooded recirculating type. The refrigeratingportion of the evaporator includes a header I3, which is positioned nearthe top of the rear vertical wall 8. The evaporator includes continuoustubing l4 arranged in generally serpentine form and secured to thesupporting wall structure. One end of the continuous tubing it isconnected at E5 to the header l3 at a point below the normal level ofthe liquid refrigerant, indicated at his, in the header. The other end[6 of the continuous tubing M is connected in communication with theinterior of the header l3 above the normal level of "liquid refrigeranttherein. By this arrangement, liquid refrigerant flows from the headerto the tubing it through the connection at l5 and vaporized refrigerantis discharged into the header at I6. The continuous serpentine tubing Mincludes a first portion or section i! which is arranged in a generallyhorizontal plane and is secured to the lower surface of the bottom Wall1 of the wall structure in any suitable mannor, as by brazing orwelding. The tubing further includes a second portion or section I8which is arranged in series with the first portion I1. The secondportion, in the form illustrated, extends in heat exchange engagementwith the rear wall 8, the end walls I and II, and the top wall 9 of thewall structure. The tubing of the second portion I8 is secured to theexterior surfaces of these walls in any suitable manner, as by brazingor welding.

Liquid refrigerant is supplied from the header to the first portion I!of the continuous tubing I4 through a vertical section I9. The tubing isformed to provide a trap 23 at the bottom of the vertical section I9,immediately preceding the beginning of the first portion I1 of thetubing. This trap includes one vertical leg 2| aligned with the verticalsection IS, a horizontal section 22, and a second vertical leg 23. Therefrigerating system includes a condensing unit (not shown) and liquidrefrigerant is supplied from the condensing unit to the evaporatorthrough a capillary tube 24. The capillary tube 24 is connected to thetubing M at the beginning of the first or horizontal portion I1 thereof.The end of the capillary tube 24 is formed as an injector to injectliquid refrigerant into the evaporator circuit in the direction of thenormal circulation of liquid refrigerant in the evaporator.

The evaporator 6 and the tubing l4 thereof are exposed to the air withinthe food storage compartment during operation of the refrigerator. Inorder to maintain a sufficiently low temperature in the food storagecompartment 3, and in order to maintain a temperature within thecompartment I2 sufficiently low for the preservation of frozen foods,evaporators of this type are normally operated at a temperaturesubstantially below the freezing point of water. As a result, moisturein the air within the food storage compartment condenses on theevaporator and collects thereon as frost, eventually forming a blanketof such frost over the tubing and the walls of the evaporator. Thisfrost acts as an insulating medium, reducing the cooling effect of theevaporator and reducing the efficiency of the refrigerating system. Itis desirable, therefore, to remove this blanket of frost from time totime to maintain the operation of the refrigerating system at areasonably high efficiency. In the embodiment illustrated, heat issupplied to the evaporator for vaporizing refrigerant within the tubing,so that the vaporized refrigerant, as it recondenses, gives up heat tothe tubing for melting the frost therefrom. Specifically, a heater ispositioned in heat exchange relationship with two spaced sections 26 and21 of the continuous tubing M. The heater may be any type of devicesuitable for supplying heat to the tubing and to the liquid refrigeranttherein; for example, it may be the sheathed insulated type ofelectrical heating element sold under the trade name Calrod.

During normal operation, refrigerant circulates through the tubing I4 ofthe evaporator in a direction indicated by the arrows, liquidrefrigerant being supplied from the header to the vertical section I9and vaporized refrigerant returning to the header l3 at the point I6.Vaporized refrigerant returns from the heater to the condensing unitthrough a suction line 28. Under such normal operation, the trap 20assists in maintaining proper direction of circulation of refrigerant,and the proper direction of circulation of the refrigerant is furtherassisted, as mentioned above, by the injecting arrangement from thecapillary tube 24 into the tubing l4. The

arrangement thus far described is not our invention but is described andclaimed in the copending application of Ralph E. King and Harley E.Bixler, Serial No. 261,174, filed December 12, 1951, now Patent No.2,665,567, issued January 12, 1954, and assigned to the General ElectricCompany, the assignee of the present invention.

During normal operation, intermittent pressure drops in such a systemmay under some conditions cause surging up the vertical section l9 andinto the header and the suction line. This situation may be particularlyacute under ice freezing conditions, where the freezing trays are placedon the bottom wall of the evaporator, resulting in a greater tendencytoward surging up the vertical section I9. Similarly, under defrostingconditions described below there may be a tendency toward surging ofrefrigerant up the vertical section I9 and into the header and thesuction line. In accordance with the present invention, such surging isminimized by the provision of a check valve 29 in the vertical leg 23 ofthe trap 20 adjacent the first or horizontal section [1 of the tubingl4, or, expressed in another way, the check valve is disposed betweenthe trap 20 and the first or horizontal portion I1 of the tubing l4.

The structure of the check valve is shown in detail in Fig. 3. The checkvalve includes a sleeve 30 connecting the leg 23 of the trap 20 and theend of the portion I1 of the tubing. The sleeve 30 is secured to the leg23 and to the tubing in any suitable manner, as by brazing or welding.The valve body 3| is mounted within the sleeve 30, being secured to thesleeve in any suitable manner, for example, by welding, Deening, etc.The valve body 3| includes an upper hollow cylindrical member 32 and acomplementary lower member 33. Members 32 and 33 are threadedly engagedto form the valve body 3|. The lower member 33 includes an opening 34centrally located therein. The portion of the member 33 adjacent theopening 34 provides a valve seat 35. The upper member 32 includes aplurality of openings 36 providing for passage of refrigeranttherethrough. A ball valve 31 is disposed within the chamber 38 formedby the members 32 and 33. This ball valve 31 is biased by gravity intoengagement with the valve seat 35 to close the opening or passage 34,blocking flow of refrigerant in a downward direction through the valve29. When a sufficient differential pressure exists, the ball valve 31 ismoved upwardly away from the seat 35, affording flow of refrigerantupwardly through the check valve 29. Even if the ball valve 31 is movedunder the differential pressure into engagement with the upper member32, upward flow of refrigerant through the valve 29 is not blockedsince, because of the provision of the plurality of spaced openings 36in the upper member, the ball valve 31 cannot close all the openingstherethrough.

During the normal operating cycle, any intermittent pressure variationsthat would ordinarily cause surging of refrigerant up the verticalsection I9 and into the header I3 and the suction line 28 insteadresults in movement of the ball valve 31 into engagement with the valveseat 35. For example should freezing trays be placed in heat exchangerelationship with the horizontal portion I1 of the tubing, the increasein vaporization of refrigerant in the portion I1 because of therelatively warm water in the trays effects a slight increase in thepressure in this portion of the tubing. This increase in pressure causesp "an w the ball valve .31 to seat, preventing any surge up the verticalsection It. The vaporized refrigerant, therefore, must proceed in thedirection of the arrows upwardly through the portion I8 to the topof-the evaporator. As the vaporized refrigerant flows upwardly in thismanner, it causes a decrease in the density of. refrigerant in theupwardly extending portions along the sides and back of the evaporator.When the density has been decreased sufficiently, the liquid refrigeranthead in the header and thevertical sectionie forces the ball valve 3']from its seat, allowing circulation of liquid refrigerant from theheader into the tubing [4 in the direction of the arrows. The abovearrangement insures that all circulation of refrigerant during thenormal operating period is through the first portion i1 and upwardlythrough the second portion l8 along the ends, back and top in thedirection of the arrows, resulting in excellent refrigeration of allportions of the evaporator.

When it is desired to defrost the evaporator, heat is supplied by theheater 25 to the tubing M at the sections 26 and 21 thereof which arespaced along the series circuit of the tubing. Liquid refrigerantvaporized by the heater circulates through the tubing I4, and therecondensation of the vaporized refrigerant effects melting of frostfrom the tubing. During the defrost operation, with the refrigeratingunit de-energized and the heater 25 energized,.the vaporization ofrefrigerant in the portion IT by the heater causes an increase inpressure in the portion H and forces the ball valve 31 into engagementwith its seat 35. This blocks surging of refrigerant upwardly throughthe vertical section l9 and into the header I3 and the suction line 28.The vaporized refrigerant is therefore forced to flow through theportion IT and upwardly in the direction of the arrows through theportion l8 to the top of the evaporator and into the header it. As inthe case of normal operating conditions, this upward flow of vaporizedrefrigerant through the upwardly extending portion [8 along the ends andback of the evaporator causes a decrease in the density of refrigerantin the portion 18. Ultimately this decrease in density is sufficientthat the pressure exerted by the liquid refrigerant in the verticalsection [9 and the header l3 exceeds the pressure exerted on theopposite side of the check valve and the ball valve 31 is moved upwardlyfrom its position shown in Fig. 3 to afford fiow of liquid refrigerantdownwardly through the vertical section If! and into the first portionI! of the evaporator. This insures a fresh supply of liquid refrigerantto the region adjacent the heater. Subsequent vaporization of thisrefrigerant, circulation thereof through the continuous tubing [4 andrecondensation thereof in this tubing M effects removal of frosttherefrom. It has been found that the time required for defrosting underidentical frost conditions is reduced by provision of the check valve 29because of the improvement in desired flow of refrigerant and in themaintenance of a supply of liquid refrigerant to the tubing in theregion of the heater 25.

For purposes of illustration, our invention has been shown applying to arefrigerating system such as that disclosed in the aforementioned Kingand Bixler application. So illustrated it includes a heater 25 whichsupplies heat to the tubing M at two points spaced along the seriescircuit thereof. It will be apparent, however, that the application ofour invention is not tion has been disclosed, it is not desired thatthis 7 invention be limited to the particular construction shown anddescribed and it is intended, by the appended claims, to cover allmodifications within the spirit and scope of this invention.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

l. A flooded recirculating evaporator comprising a header and continuoustubing connected at both ends to said header, said tubing depending fromsaid header, one end of said tubing being connected to said header belowthe level of liquid refrigerant therein, said one end including avertical section for supplying liquid refrigerant from said header, theother end of said tubing being connected to said header above the levelof liquid refrigerant in said header, said tubing being formed toprovide a trap between said vertical section and the remainder of saidtubing, said trap extending below said remainder of said tubing, aheater disposed in heat exchange relationship with a section of saidremainder of said tubing, a check valve between said trap and saidremainder of said tubing, said check valve including a hollow valve bodyhaving a valve seat in the lower portion thereof, and a ball valvewithin said valve body gravity-biased into engagement with said seat toblock flow of re frigerant downwardly through said valve whereby surgeof refrigerant upwardly in said vertical section toward said header isblocked.

2. A flooded recirculating evaporator comprising a header and continuoustubing connected at both ends to said header, said tubing depending fromsaid header, one end of said tubing being connected to said header belowthe level of liquid refrigerant therein, said one end including avertical section for supplying liquid refrigerant from said header, theother end of said tubing being connected to said header above the levelof liquid refrigerant in said header, a trap between said verticalsection and the remainder of said tubing extending below said remainderof said tubing, said trap including one vertical leg in alignment withsaid vertical section, a horizontal leg and a second vertical legarranged to communicate with said remainder of said tubing, a heater inheat exchange relationship with a section of said remainder of saidtubing, and a check valve in said second vertical leg of said trapadjacent said remainder of said tubing for blocking surge of refrigerantupwardly in said vertical section toward said header.

3. A. flooded recirculating evaporator comprising a header andcontinuous tubing connected at both ends to said header, said tubingdepending from said header, said tubing including a horizontal firstportion and a second portion in series with said first portion andextending upwardly therefrom, one end of said tubing being connected tosaid header below the level of liquid refrigerant therein, said one endincluding a vertical section communicating with said first portion forsupplying liquid refrigerant to said first portion, said second portionof said tubing being connected to said header above the level of liquidrefrigerant in said header, a trap between said vertical section andsaid first portion of said tubing extending below said first portion,said trap including one vertical leg in alignment with said verticalsection, a horizontal leg and a second vertical leg arranged tocommunicate with said first portion, a heater in heat exchangerelationship with a section of at least one of said portions of saidtubing, a check valve in said second vertical leg of said trap adjacentsaid first portion, said check valve including a hollow valve bodyhaving a valve seat in the lower portion thereof, and a ball valvewithin said valve body gravity-biased into engagement with said seat toblock flow of refrigerant downwardly through said valve whereby surge ofrefrigerant upwardly in said vertical section toward said header isblocked.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,926,384 Hull Sept. 12, 1933 2,008,628 Ruff July 16, 19352,040,744 Hull May 12, 1936 2,138,612 Philipp Nov. 29, 1938 2,665,566Grimshaw Jan. 12, 1954

